Spectrophotometric determination of vitamin A in oils and fats

A spectrophotometric method for determining vitamin A based on interaction with 50% trichloroacetic acid solution in dichloromethane was developed. The blue reaction product had a maximum absorption at 620 nm and obeyed Beer's law over the concentration range of 0.5-5.0 microgram retinol/ml solution. The molar absorptivity of the reaction product was 1.58 X 10(5). As much as 100 microgram vitamin D2, and beta-carotene up to 12 times the vitamin A concentration, did not interfere with the determination. The results obtained from the determination of vitamin A in cod liver oil and butter showed excellent agreement with the Carr-Price method, 43.013(d).